1. Field of the Invention
The present invention generally relates to a contactor for electronic parts and, more particularly, to a contactor for electronic parts which contactor provides electrical conduction by contacting an electrode of a semiconductor device, such as an LSI circuit, to test the semiconductor device, and to a testing method using such a contactor.
Recently, a manufacturing technology of a semiconductor substrate and the like has been remarkably developed. Accordingly, a wiring pattern of a semiconductor device, such as an LSI circuit, has become finer, and terminals have been remarkably increased in number and miniaturized.
Also, miniaturization and high-density packaging are required for an electronic device using the semiconductor devices. For example, production and sales of mobile devices, such as a cellular phone, a mobile PC and a video camera, which are required to be small and of high performance are sharply increasing. Also, a need for a highly efficient computer having a minimum distance between adjacent LSI terminals to ensure a high-speed operation is increasing.
Therefore, more and more semiconductor devices such as the LSI circuit are shipped in the form of an unpackaged LSI chip with its function guaranteed. Such a shipping is referred to as a KGD (Known Good Die). Also, a number of shipping chip-size-packages (CSP), which are semiconductor devices packaged in the same size as the LSI chip, is sharply increasing.
In these circumstances, in order to conduct a test for the semiconductor devices such as the LSI circuit, a supply of a contactor capable of surely conducting electrically with a multitude of terminals formed as a part of the finer wiring pattern is becoming essential.
Also, from the viewpoint of efficiency in LSI tests, there is an ever-increasing need to conduct all of tests, such as an FT (Final Test) and a BI (Burn-In test), for a plurality of LSIs in the form of a wafer formed in an LSI manufacturing process.
A full test in the form of a wafer has an advantage of better handling efficiency than testing a separate LSI chip. That is, if each chip has a different size, a handling facility cannot be used commonly. However, in the form of a wafer, since the external shape of the wafers is standardized, the wafers can be conveyed all at once. There is also an advantage that information of inferior chips can be administered with a wafer map.
Further, for a wafer-level CSP which has recently been developed, even a packaging process can be controlled by the unit of a wafer. Therefore, if a test in the form of a wafer can be realized, LSI circuits can be treated in the form of a wafer from a wafer process through the packaging process to the tests. This makes the LSI manufacturing process efficient.
Hence, it is desired, as mentioned above, that a contactor capable of contacting a plurality of terminals of LSI circuits all at once be developed, the LSI circuits being in the form of wafer and having a multitude of miniaturized pins.
2. Description of the Related Art
Conventional contactors used for testing LSI circuits include: 1) a contactor using a mechanical probe of a needle type; 2) a contactor using a membrane probe; and 3) a contactor using an anisotropic conductive rubber.
1) A contactor using a mechanical probe of a needle type:
The contactor using a mechanical probe of a needle type is formed by placing each of needles (formed of such a material as a tungsten wire) at a position on a contactor substrate, the position corresponding to a terminal of an LSI circuit to be tested. Generally, each of the needles is slant from upright, extending toward the terminal of the LSI circuit. However, a method whereby each of the needles is placed upright has been developed.
2) A contactor using a membrane probe:
The contactor using a membrane probe is formed as a circuit substrate in the form of a film, the circuit substrate having a metal protrusion (referred to as a bump hereinafter) as a contact electrode for use as a stylus.
3) A contactor using an anisotropic conductive rubber:
The contactor using an anisotropic conductive rubber is formed of a rubber as an insulating member and a material (such as a metal wire) embedded therein, the material being conductive only in a thickness direction (perpendicular direction).
1) The contactor using a mechanical probe of a needle type has the following problems:
a) A manufacturing cost of the contactor is high, because the needles are formed one by one.
b) A location precision is subject to a limit, because the needles are individually mounted on the contactor substrate.
c) In a case of forming each of the needles to be slant, an arrangement of the needles is subject to a limit. Thus, it is difficult to manufacture the contactor capable of contacting a plurality of LSI circuits all at once.
2) The contactor using a membrane probe has the following problems:
a) Each of the contact electrodes cannot move freely. Since each of the contact electrodes is embedded in an insulating substrate, each of the contact electrodes can move only within a small range. Also, because the contact electrode is a metal bump, the contact electrode lacks flexibility. Therefore, when adjacent bumps have different heights, the lower bump does not contact the corresponding terminal or causes a poor connection.
b) Since the bump as a contact electrode is generally formed by laminating metal plating layers, manufacturing the bump takes a long time and the bump cost is high.
3) The contactor using an anisotropic conductive rubber has the following problems:
a) The contactor using an anisotropic conductive rubber has a short life duration. Especially, when used at a high temperature, the rubber part undergoes plastic deformation. Therefore, the contactor using an anisotropic conductive rubber can only be used 20 to 30 times at best and only once at worst.
b) Since it is difficult to embed the conductive materials with a fine pitch into the rubber, the contactor using an anisotropic conductive rubber cannot be used to test an LSI circuit having terminals with a fine pitch. This contactor can only be used to test an LSI circuit having terminals with approximately a 150 μm or greater pitch.
Further, in a case of using a contactor to test wafer-level LSI circuits all at once, a number of terminals of the LSI circuits sometimes totals several tens of thousands (100,000 terminals). Thus, the above-mentioned contactors commonly have the following problems.
I) A great pressure is required to press the contactor against the terminals of the LSI circuits.
With the above-mentioned conventional contactors, a pressure of 0.1 N (approximately 10 grams) a terminal is required. Therefore, in a case where a wafer has 100,000 terminals, a pressure of 10,000 N (approximately 1,000 kilograms) is required. With the conventional contactors, because of the different heights of the electrodes and other reasons, it is difficult to impose a pressure on all of the terminals uniformly. Thus, an excessive pressure is sometimes imposed on particular terminals. Additionally, without a facility that accepts all the pressure, there is a risk that the wafer may be broken or bent so that a circuit on the LSI chip is damaged.
II) Different coefficients of thermal expansion cause undesired shifting.
In most cases, a wafer for LSI circuits is made of silicon. A coefficient of linear expansion thereof is approximately 3 ppm. On the other hand, the insulating substrate of each of the above-mentioned contactors is formed of a resin or a rubber material, and a coefficient of linear expansion thereof is approximately 13–30 ppm. Therefore, even though the contactor accurately contacts the terminals of the LSI circuits at a normal temperature, when put at a high temperature as in the BI test, there is a risk that different coefficients of thermal expansion between the material forming the insulating substrate of the contactor and the silicon material of the wafer cause the contact electrode to shift so that the contact electrode is detached from the corresponding terminal of the LSI circuit or contacts an adjacent terminal. In a case where the insulating substrate of the contactor is formed of polyimide, a coefficient of thermal expansion of the polyimide is approximately 13 ppm. Thus, even though the contactor accurately contacts the terminals of the LSI circuits at a normal temperature, when heated to a temperature of 125° C., the contactor electrode is shifted from the corresponding terminal by as much as 100 μm around the outermost periphery, when using an 8-inch wafer (approximately 100 mm in diameter).